1. Field of the Invention
The present invention relates to a sealed semiconductor device and a lead frame used for the sealed semiconductor device, particularly to a sealed semiconductor device holding the interval between an internal lead and a semiconductor chip almost constant and a lead frame used for the sealed semiconductor device.
2. Description of the Background Art
An LOC (Lead On Chip) semiconductor device is described below as an example of conventional sealed semiconductor device obtained by sealing a semiconductor chip with a resin. In the LOC semiconductor device, a pad is formed nearby the center of a semiconductor chip and an internal lead extending to the vicinity of the pad is provided. Therefore, the LOC semiconductor device has an advantage that a larger semiconductor chip can be mounted compared to a structure of bonding a wire to a lead located at the side face of the semiconductor chip.
As shown in FIG. 28, in the case of an LOC semiconductor device, a semiconductor chip 101 is fixed on a die pad 103 through a die pad material 104. A lead 102 which includes an internal lead 102a extends to the vicinity of a pad (not illustrated) on the semiconductor chip 101. The tip end of the internal lead 102a and the pad are wire-bonded by a gold wire 105. Then, the semiconductor chip 101 and the internal lead 102a are sealed with a molded resin 106.
In the case of this LOC semiconductor device, however, as shown in FIG. 29, when setting the semiconductor chip 101 and internal lead 102a in a mold and sealing them with the mold resin 106, the semiconductor chip 101 maybe shifted toward the internal lead 102a due to the difference in flow resistance between a mold resin 106a flowing by the upper side of the semiconductor chip 101 and a mold resin 106b flowing by the lower side of the semiconductor chip 101.
Therefore, the internal lead 102a and the surface of the semiconductor chip 101 are excessively close each other, the capacitance between them fluctuates, and thereby timing of an input signal and an output signal may be shifted.
As the LOC semiconductor device for preventing the internal lead 102a and the surface of the semiconductor chip 101 from being close each other when sealed by a mold resin, there is an LOC semiconductor device disclosed in Japanese Patent Laying-Open No. 6-169052. In the case of the LOC semiconductor device, an insulating layer 107 is formed between a semiconductor chip 101 and an internal lead 102a as shown in FIG. 30.
The insulating layer 107 is continuously formed along the direction in which the internal leads 102a are arranged (direction almost orthogonal to the paper surface) so as to be present between every internal lead 102a and the semiconductor chip 101. The gaps between each internal lead 102a and the insulating layer 107 and between the insulating layer 107 and the semiconductor chip 101 are fixed by an adhesive.
According to the LOC semiconductor device, the semiconductor chip 101 is not shifted toward the internal lead 102a when sealed by a mold resin because the insulating layer 107 is formed between the semiconductor chip 101 and the internal lead 102a. 
Thereby, fluctuation of the capacitance between the internal lead 102a and the surface of the semiconductor chip 101 because the leads are excessively close each other is prevented and it is possible to control the shift of timing between an input signal and an output signal.
However, the LOC semiconductor device disclosed in Japanese Patent Laying-Open No. 6-169052 has the following problem. In the case of this LOC semiconductor device, to bond the insulating material 107 with the semiconductor chip 101, it is necessary to press the internal lead 102a against the semiconductor chip 101 from the upper side at an temperature of 150 to 200xc2x0 C. or press the semiconductor chip 101 against the internal lead 102a from the upper side by vertically reversing the internal lead 102a and the semiconductor chip 101.
Therefore, a production system for pressing the internal lead 102a or semiconductor chip 101 is necessary and thereby, the production cost may increase.
Moreover, though the insulating material 107 generally uses a resin film, the resin film generally has a high hygroscopicity. The moisture absorbed in the insulating material 107 is evaporated due to heat when mounting a semiconductor device sealed by the resin on a substrate. In this case, cracks may occur on the mold resin 106.
Particularly, the insulating layer 107 absorbs much moisture because the layer 107 is continuously formed along the direction in which internal leads 102a are arranged (direction almost perpendicular to the paper surface) and has a comparatively large contact area with the internal leads 102a and semiconductor chip 101. Therefore, when the moisture is evaporated, cracks tend to more easily occur in the mold resin 106.
The present invention is made to solve the above problems, and it is an object of the present invention to provide a sealed semiconductor device capable of easily preventing an internal lead and a semiconductor chip from being excessively close each other without using any additional production system when the device is sealed by a mold resin and controlling cracks from being generated on the mold resin due to the heat when the device is set to a substrate and the like and it is another object to provide a lead frame used for the sealed semiconductor device.
A sealed semiconductor device according to an aspect of the present invention is a sealed semiconductor device having a semiconductor chip portion and a lead frame portion including an internal lead portion extending onto the surface of the semiconductor chip portion and moreover having a holding member for holding the semiconductor chip portion and the internal lead portion at a predetermined interval by being fixed to either of the semiconductor chip portion and internal lead portion and contacting the other without being fixed.
According to the above sealed semiconductor device, it is possible to comparatively easily prevent an internal lead portion and a semiconductor chip portion from excessively close together when sealed by a mold resin without using an additional system for fixing a holding member to the semiconductor chip portion and internal lead portion, compared to the case of a conventional sealed semiconductor device because the holding member is fixed to either of the semiconductor chip portion and internal lead portion and contacts the other without being fixed.
It is preferable that the above holding member includes a tape member bonded and fixed to the internal lead portion and particularly preferable that the tape member is set in areas around the semiconductor chip portion.
In this case, because the contact area between the tape member and semiconductor chip portion is greatly decreased compared to the case of a conventional sealed semiconductor device, the quantity of moisture to be absorbed by the tape member is also reduced. Thereby, it is possible to control cracks from being generated on a mold resin in accordance with evaporation of moisture.
It is preferable that the holding member includes a first protrusion protruding toward the semiconductor chip portion provided to the internal lead portion and particularly preferable that the first protrusion is formed by bending the internal lead portion.
In this case, it is possible to prevent the internal lead portion and semiconductor chip portion from being excessively close each other by bending the internal lead portion without using an additional member.
It is more preferable that the crest portion of an internal lead contacts the semiconductor chip portion because the lead is bent.
In this case, it is possible to control damages from occurring on the surface of the semiconductor chip.
Moreover, it is preferable that the internal lead portion includes an original internal lead and a dummy internal lead electrically connected with the semiconductor chip portion and its first protrusion is formed in the dummy internal lead.
When the first protrusion is formed on the original internal lead, the first protrusion damages the surface of the semiconductor chip portion when wire-bonding is carried out. However, it is possible to prevent the damage by forming the first protrusion on the dummy internal lead on which wire-bonding is not carried out.
It is preferable that the semiconductor chip portion is almost rectangular, the original internal lead is set toward a pad portion formed nearby the center of the almost-rectangular semiconductor chip portion from a pair of faced sides of the semiconductor chip portion, the dummy internal lead is set toward the semiconductor chip portion from another pair of sides facing the direction almost orthogonal to the pair of faced sides.
In this case, because dummy internal leads are arranged as a lead frame used for a sealed semiconductor device separately from a series of patterns of original internal leads, it is controlled that the pattern of original internal leads is restricted by the pattern of dummy internal leads.
It is more preferable that the first protrusion contacts an area around the semiconductor chip portion.
In this case, it is possible to control damages to the semiconductor chip portion.
It is still more preferable that the semiconductor chip portion includes a semiconductor chip body and a die pad for mounting the semiconductor chip body and the first protrusion contacts the die pad.
In this case, it is possible to completely eliminate damages to the semiconductor chip portion.
It is still more preferable that the semiconductor chip portion includes a semiconductor chip body and a die pad for mounting the semiconductor chip body and a holding member includes a second protrusion fixed to the die pad and protruding toward the internal lead portion.
Also in this case, it is possible to prevent the semiconductor chip portion and internal lead portion from being excessively close each other without damaging the semiconductor chip portion.
It is still more preferable that the holding member is at least located at the opposite side to the injection port of the mold resin when sealing the semiconductor chip portion and internal lead portion with the mold resin.
In this case, it is possible to stably receive the force for the mold resin flowing through the opposite side to the side where internal leads of the semiconductor chip portion are arranged to press the semiconductor chip against the side where internal leads are arranged by setting the holding member to a portion to be most displaced by the force.
A lead frame according to another aspect of the present invention is a lead frame used for a sealed semiconductor device obtained by sealing the above semiconductor chip portion with a mold resin, which is provided with an internal lead portion and a holding lead portion. The internal lead portion is set toward a pad portion formed nearby the center of the semiconductor chip portion and electrically connected with the pad portion. The holding lead portion holds the semiconductor chip portion and the internal lead at a predetermined interval by contacting the semiconductor chip portion.
The lead frame makes it possible to easily prevent the semiconductor chip portion from being excessively close to the internal lead due to the flow of a mold resin when injecting the mold resin by the holding lead portion without using any additional member.
It is preferable that the holding lead portion includes the internal lead portion and a tape member is bonded and fixed to a position of the holding lead portion corresponding to the area around the semiconductor chip portion.
In this case, because the contact area between the tape member and the semiconductor chip portion is greatly decreased, the quantity of moisture to be absorbed by the tape member is also reduced. Thereby, it is possible to control cracks from being generated on the mold resin due to evaporation of the moisture after sealing with the mold resin.
It is more preferable that the holding lead portion is a dummy internal lead portion.
In this case, because dummy internal leads are not wire-bonded, it is possible to prevent the semiconductor chip portion from being damaged.
It is still more preferable that internal leads are arranged toward a pad portion formed nearby the almost-rectangular semiconductor chip portion from a pair of faced sides of the almost-rectangular semiconductor chip portion and the holding lead portion is set toward the semiconductor chip portion from another pair of sides facing the direction almost orthogonal to the pair of faced sides.
In this case, because dummy internal leads are arranged separately form a series of patterns of original internal leads, it is controlled that patterns of the original internal leads are restricted by patterns of dummy internal leads.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.